My testing indicates this is the problem area. I removed C18 and the problem went away. Obviously, as Bill indicated, this is not a fix. ? I think that the state of the switches (U1, U8, U3, U7) in SSB should match the state of the switches in CW. They do not.?
dave
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On Mar 22, 2025, at 1:40?PM, Oliver KI3P via groups.io <oliver@...> wrote:
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The situation I think we might have is that both TX_BPF_SEL and RX_BPF_SEL are HIGH during SSB transmit. This lets a little bit of the transmitted signal leak through the TR switch back into the amplifier input through the BPF selection stage, like this:
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These two lines are controller by GPIO register bank A:
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This register is set by the function call ; the code there looks correct and unchanged. Scanning the code, it all appears to be correct. Some judiciously placed statements like this will confirm:
Debug("Set LPF GPA state: "+String(LPF_GPA_state,DEC));
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The fix that I implemented (major change to radio layout) to cure the short that caused the burning smell has created a display freeze issue, so I'm not able to test this myself right now.
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